The subject matter disclosed herein relates to a fuel injector, and particularly to a fuel injector having a mixing circuit positioned within an injector body to create an air-fuel mixture.
Gas turbines usually burn hydrocarbon fuels and produce air polluting emissions such as oxides of nitrogen (NOx) and carbon monoxide. Oxidization of molecular nitrogen in the gas turbine depends upon the temperature of gas located in a combustor, as well as the residence time for reactants located in the highest temperatures regions within the combustor. Thus, the amount of NOx produced by the gas turbine may be reduced by either maintaining the combustor temperature below a temperature at which NOx is produced, or by limiting the residence time of the reactant in the combustor.
One approach for controlling the temperature of the combustor involves premixing fuel and air to create a lean air-fuel mixture prior to combustion. This approach includes the development of fuel injection where the air-fuel mixture is injected into and mixed with a main flow of high energy fluid from the combustor. Specifically, the air-fuel mixture becomes entrained with the main flow of high energy fluid before ignition. This approach results in increasing the consumption of fuel, which in turn reduces the air polluting emissions.
A secondary fuel injector may be provided to inject the air-fuel mixture into the main flow from the combustor. Specifically, for example, the secondary fuel injector may include outer fuel injection as well as inner fuel injection. However, the inner fuel injection may produce relatively high NOx emissions, as a diffusion flame created by the inner fuel injector generally has an elevated flame temperature.